F23 System Wide Change: Default Local DNS Resolver

[Florian Weimer]

On 06/01/2015 10:57 PM, Andrew Lutomirski wrote:

> This is glibc we're talking about, though.  Have you tried to get a
> glibc bug fixed?  It's not a pleasant experience.

It is possible, but it requires effort.  Admittedly, sometimes that
effort appears disproportionate to what is being fixed.

In this particularly case, only *very* few people are familiar with
resolv/, and test coverage for that part is extremely poor.

> For example, the bug I reported has a candidate patch.  That patch
> isn't applied, and the patch looks like the bug might be a security
> issue.  It's been in that state for months.  This is not unusual for
> glibc.

Can you explain why you think it is a security issue?

In any case, the impact from accidentally triggering this bug seems more
severe.

> Anyway, even on a LAN, the overhead of a network round trip per
> cacheable DNS query may be non-negligable for some use cases.  A local
> caching resolver fixes that, too.

Right, and it isolates resolvers from the impact of buggy application
which enter an infinite loop if a service becomes unavailable (i.e.,
they do a new DNS lookup for each refused TCP connection).

-- 
Florian Weimer / Red Hat Product Security